I also agree that the answer is B: whom
in this sentence you are using the preposition + whom grammar structure. Whom is considered an object pronoun and is used when asking who will receive the action, which in this case, I believe is, baking those cookies. Hopefully this makes sense and good luck.
Answer and Explanation:
I'll provide an answer against the statement "The fast-food industry can give valuable work experience to teenagers.”
The fast-food industry is not at all concerned with the value the experience of working in it will add to someone's life. As was stated in the text, they hire teenagers "because they are less expensive to hire than adults, but also because their youthful inexperience makes them easier to control." The experience those workers will acquire from that job is limited, probably even useless in other areas. A McDonald's employee does not learn how to cook - they can't leave McDonald's to suddenly work at a regular restaurant. They have machines beeping all around them, letting them know when the food is supposed to be ready.
